An engagement ring is seen on the finger of Mary Elizabeth Donaldson as she sits next to His Royal Highness Crown Prince Frederik of Denmark during a press conference at Fredensborg Castle October 8, 2003 in Copenhagen, Denmark. The pair announced their engagement, with the wedding set for May 14, 2004.Scott Barbour
/ Getty Images

Camilla Parker Bowles shows off her engagement ring as she and Prince Charles arrive for a party at Windsor Castle after announcing their engagement in February 2005.John Stillwell
/ AFP/Getty Images

Leitizia Oritz Rocasolano shows off her ring during an official engagement ceremony at the garden of El Pardo Palace November 6, 2003 at Palacio del Pardo in Madrid, Spain.Carlos Alvarez
/ Getty Images

An engagement ring is seen on the hand of Crown Princess Victoria of Sweden as she and Mr. Daniel Westling announced their engagement during a press conference at The Royal Palace on February 24, 2009 in Stockholm, Sweden.Patrik Osterberg
/ Pool/Getty Images

Marie Cavallier shows her engagement ring during a press conference attended with Prince Joachim of Denmark to announce their engagement, at the Riddersalen (Great Hall) of the Amalienborg Palace on October 3, 2007 in Copenhagen, Denmark.Niels Henrik Dam
/ Getty Images

Zara Phillips, daughter of Princess Anne, and grand-daughter of Britain's Queen Elizabeth II, shows the photographer her engagement ring as she poses for a photograph with her fiance, England rugby player Mike Tindall, after the announcement of their engagement, at their home in Gloucestershire, south west England on December 21, 2010.Tim Ireland
/ AFP/Getty Images

A close-up photo of an engagement ring worn by Charlene Wittstock, fiancee to His Serene Highness, Prince Albert II Of Monaco visits the National Museum during a State visit on April 4, 2011 in Dublin, Ireland.Gareth Cattermole
/ Getty Images